It is well known in the semiconductor art to manufacture and use so-called hybrid integrated circuits. These hybrid integrated circuits contain a number of circuit elements including LSI'S, chips and other devices which are in turn mounted on a printed circuit board. Typically, the hybrid integrated circuits comprise a ceramic substrate which is connected to the main circuit using input/output pins which are either pushed into the main circuit board for the connections or are mounted using surface technology onto the main circuit board. Conventional circuit boards for hybrid integrated chips are illustrated in "Ceramic Substrates For Functional Circuits" (Kogyo-Chosa-kai, Aug. 10, 1985, page 57) and in "A Handbook of Hybrid microelectronics" (Kogyo-Chosa-kai, Aug. 20, 1989, page 56). FIG. 9 illustrates a conventional printed circuit board used for hybrid integrated circuit chips which comprises a substrate 31, wiring layer 32, first conductors 33, insulators 34, through-holes 35, pins 36 and second conductors 37. The wiring layer 32 includes first conductors 33-and the insulators 34.
In the conventional hybrid integrated circuit printed circuit board, the through-holes 35 and the second conductors 37 are formed in the substrate 31. Formed on this substrate 31 by film forming techniques such as plating or sputtering, are first conductors 33 and, by photolithography and etching, are insulators 34 which thus produce wiring layer 32. Usually, the first conductors 33 consist of copper and the insulators 34 of polyimide although other conducting materials and insulators may be used. The first and second conductors 33 and 37 are connected to each other. Subsequently, pins 36 are attached to the substrate 31. The second conductors 37 are electrically conductive of the pins 36. The input/output signals are supplied to and emitted from the printed circuit board through the pins 36.
In the conventional hybrid integrated circuit board the pins 36 have a diameter not less than approximately 0.5 millimeters so that it is difficult to arrange a large number of them on a substrate 31. That is, the physical size of the pins restricts the number of input/output pins which can be utilized thereby limiting the complexity of the circuitry which can be carried by the hybrid integrated circuit chip since insufficient inputs and outputs are available. This further reduces the number of active devices which can be moderate in the hybrid integrated circuit chip thereby restricting the potential advantages of these devices. Moreover, jigs are employed when-,collectively attaching pins 36 to a substrate. For each different type of wiring pattern a different set of jigs must be used to attach the pins. This also creates unnecessary complexity in assembling the finished electronic device into which the hybrid integrated circuit chip is to be incorporated.
Accordingly, a need continues to exist for printed circuit board for hybrid integrated circuits which can be fabricated in high productivity and which is a large number of input/output terminals to allow high density mounting. In particular, need continues to exist for printed circuit board for hybrid integrated circuits having a high density of input/output terminals.